**Important** Visa

So, this is a very important post for any future Light Fellows who, like me, want to do some combination of summer and academic year at two different programs.
Since you're allowed to be in Japan for up to 90 days as a tourist, or "temporary visitor" without a visa, for the summer programs like HIF a visa is not necessary. For a year-long program like IUC a visa is necessary, but the staff there are prepared for this, and will help you get whatever type of visa is needed. However, according to IUC staff, the Ministry of Foreign Affairs website, the Japanese consulate, and pretty much anywhere else official that I looked, while one can switch from one type of visa to another (say, from "student" to "worker"), it is impossible to go from being a "temporary visitor" to having a visa without leaving Japan. Herein lay the problem.
BUT...having 1) read that sometimes if asked nicely, Japanese immigration will grant you a visa, and 2) heard from a previous Light Fellow that he had received a visa in-country...I thought it was possible that I might be able to get my visa in Japan as well (the alternative being to make a quick trip to Korea, Hong Kong, or some other nearby country with a Japanese consulate).
With that in mind, I headed over to the Yokohama Immigration Office as soon as I arrived. I had prepared a whole sob story, about how I really needed my visa and didn't have enough money/time to go to Korea, and could they please, please give me a visa in Japan... I approached the information desk nervously, ready to beg, plead, and bribe--however no sooner had I gotten out that I wanted to switch from temporary visitor to my cultural activities visa, then the man at the desk interrupted my carefully rehearsed story with a matter-of-fact "Fill out these two forms and go to the second window." And that was the end of the story. One week and 4000 Yen later, I got my visa; and at no time did anyone at Immigration seem to think that what I wanted was anything but perfectly normal.
So--The Moral of the Story:
No matter what the MOFA site and anyone you might speak to in the States says, it is 100% possible to get your visa in between programs, without leaving Japan. And I hope this tale saves any future Light Fellows the stress and worry that I went through.
**P.S. Another small note: although they never actually checked mine at Customs, in order to enter Japan as a "temporary visitor," you are supposed to have proof (i.e. a ticket to somewhere) that you will be leaving Japan within 90 days. In this case, the best thing is to either buy a refundable ticket (what I did), or a ticket home that you can then change to the date you actually want to go home.